The present invention relates to a rotary table capable of indexing work stations thereon. More particularly, the invention provides a mechanism useful for stepwise incremental advancement of a turntable whereby sequential portions of the table top may be presented to appropriate tooling so that work functions may be performed.
It is well known to the skilled artisan to provide rotary mechanisms for the smooth rotary advancement of machine parts. Such devices are known as Geneva mechanisms. The usual Geneva mechanism provides a slotted plate attached to a shaft which has a plurality of slots which are successively engaged by an eccentrically mounted projecting pin secured on the edge of a drive wheel attached to a rotating member. As the driver rotates, the pin revolves and enters one of the slots and pushes the slotted plate to its next position, at which point the pin exits the slot and prepares its positioning to enter the next sequential slot. Such Geneva mechanisms are commonly employed with machine tools and indexing speed may be controlled directly by affecting driver speed.
Many types of indexing arrangements have been known in the art. U.S. Pat. No. 3,301,097 employs one example of Geneva operation. This disclosure indexes in the classic Geneva manner and the station is then locked by axial shifting caused by fluid pressure. U.S. Pat. No. 3,279,281 incrementally advances machine components wherein the drive wheel may be locked in position by activation or retraction of a drive pin. Drive is aperiodic and is actuated by a demand feed signal which is electro-magnetically controlled. Rotary motion is imparted indirectly via a drive train. U.S. Pat. No. 1,347,492 describes a use for Geneva drives in book binding production.
This disclosure employs a particular type of turn wheel having both slotted and arcuate portions whereby dwell and drive time may be more effectively controlled for this specific application. U.S. Pat. No. 2,106,109 shows a chain driven device for intermittent circular movement and provides stationary guides at the entrance and departure stations for smooth starting and stopping movement.
U.S. Pat. No. 2,049,690 provides a gear driven clutch which is controlled by external current impulses. It is taught to be useful for accumulators in calculating machines. The gears are loosely mounted on their shafts. U.S. Pat. No. 3,478,616 provides a Geneva apparatus having slotted drive and arcuate relief on the wheel. The power drive is disengaged at the midpoint of the dwell position. U.S. Pat. No. 3,093,014 provides a ratcheting indexing device. U.S. Pat. No. 3,153,952 provides an indexing mechanism where a driving means turns a Geneva wheel. A locking means which is movable along the drive axis engages the plate member. U.S. Pat. No. 1,045,102 provides a gear driven cam follower which drives a Geneva wheel. U.S. Pat. No. 2,124,213 provides intermittent gearing for Geneva drives having a lock engaged during non-driving periods. The lock eccentrically revolves around an axis parallel to the driven axis and periodically engages the driven member. U.S. Pat. No. 2,358,503 provides a turret indexing mechanism for lathes employing socket and plunger type operation.
From the foregoing discussion it is clear that various configurations of Geneva wheel indexing have been heretofore employed. In some operations it is not necessary to lock-in each position. However, it is quite apparent that for machine tool cooperation uses, it is a distinct advantage to lock the turning wheel firmly at each work station. Some of the foregoing disclosures loosely lock the work station position by means of the station turning pin itself or by use of an eccentric on the drive means axis. In contradistinction, the present invention provides a slotted, driven slide which positively blocks work station movement during dwell times.